Disc lead-in for electron tubes



Nov. 12, 1957 E. HANFT ETAL 2,813,219

DISC LEAD-IN FOR ELECTRCN TUBES Filed Sept. 30, 1952 INVENTORJ' K617126271 E Hanfi 1K" Mbbojas EPrysHli United States Patent DISC LEAD-IN FOR ELECTRON TUBES Kenneth Edward Hanft, Carlstadt, and Nicholas Edward Pryslak, Florham Park, N. J., assignors to Radio Corporation of America, a corporation of Delaware Application September 30, 1952, Serial No. 312,322 3 Claims. (Cl. 313-252) This invention relates to disc-shaped lead-ins and more particularly to a disc lead-in having a structure for ruggedly supporting an electrode and for reducing strains on a seal between the lead-in and an envelope with which it is associated.

One type of electron tube using a disc lead-in is the so-called Pencil type tube, which comprises an elongated envelope having at the ends thereof metallic electrode supports, and a tubular glass portion intermediate said ends. A metal disc is sealed coaxially across and through the tubular glass portion mentioned in glass-tometal seals, to dispose a portion of the disc inwardly of the envelope for service as a support for an electrode, and another portion outside of the envelope for utility as a contact member for connecting said electrode to a source of suitable electrical characteristic.

Several difficulties have been encountered in connection with a structural organization of the type referred to. One of these difiiculties is manifested in seal rupture as the consequence of appreciable force sometimes necessary in effecting connected and disconnected relationship of the outer portion of the disc lead-in with respect to associated circuit elements. In one utilization, the circuit element associated with the disc lead-in is a resonant line comprisinga tubular structure having inner walls with which the disc is required to make contact. In practice, the disc engages a portion of said inner walls intermediate or at least appreciably spaced from the ends of the resonant line. To secure this engagement, it is therefore necessary to insert the electron tube referred to into the resonant line with the periphery of the disc sliding along the inner surface of the line. A.

similar sliding movement is necessary when disengaging the tube from the line aforementioned. A good electrical connection between the resonant line and the disc lead-in referred to requires that the disc lead-in engage the inner surface of the resonant line with appreciable force. Since the resonant line is usually of the same diameter throughout its length, the sliding movement of the disc lead-in on connection to and disconnection from the line involves opposition to a force in a direction placing a severe burden on the seals between the lead-in and the tubular glass portion of the envelope referred to. In some instances, this force is of such magnitude as to rupture the aforementioned seals.

Another difiiculty arises during normal handling of an electron tube of the type discussed. This occurs as a consequence of the outline of the tube structure which includes an intermediate outwardly extending portion comprising the outer portion of the disc-lead-in referred to. This outwardly extending portion constitutes a projection which receives a relatively large portion of the impacts transmitted to the tube. An accidental dropping of the tube, for example, would in all likelihood result in the application of a severe blow to the outer portion of the disc lead-in, involving a force factor sulficient to rupture the seals between the lead-in and the tube envelope.

Accordingly, it is the object of the invention to provide an electron tube structure having a disc lead-in andwhich is free from the difficulties mentioned.

A further aim of the invention is to provide seals between a disc lead-in and a glass envelope and to provide a disc lead-in. structure for absorbing impacts without injury to the seals.

Another purpose of the invention is to. provide a disc lead-in having a two part structure for providing a relatively rugged support for an electrode and relatively strong seals to a glass envelope, and for absorbing impactsapplied to portions thereof outside of the envelope without harm to said seals or to its support function with respect to said electrode.

A further object of the invention is to provide a disc lead-in assembly for an electron tube having a relatively rugged central portion for supporting an electrode and for sealing across a glass envelope, and having a relatively weak and resilient portion extending from said central portion to the periphery of the lead-in assembly and being disposed externally of said envelope, for absorbing impacts applied thereto without transmitting said impacts to said rugged portion, thereby preserving seals from harm and preventing displacement of said electrode.

Another aim of the invention is to provide a disc leadin assembly having a relatively thick central portion for sealing across an envelope in relatively rugged seals, and a relatively thin annular portion extending from said central portion to the periphery of the assembly for absorbing impacts without harming said seals.

A further purpose is to provide a disc lead-in including a portion having appreciable resistance to,deformation and another portion readily responding to deformation, whereby a seal involving said first-named portion is free I from harm from impacts directed to said another poror brazing,

tion.

Another aim is to provide anelectron tube structure having an envelope and a disc lead-insealed across said envelope, the disc having a relatively rugged and nonresilient portion at the region of the seal, and having .a resilient and readily deformable portion extendingout side of said envelope for absorbing substantially all the force of impacts directed to the lead-in and for preserving saidrugged portion from impact forces capable of deforming the same, whereby said seal is preservedfrom harm.

A disc lead-in structure embodying the inventionmay include two concentric and substantially coplanarportions. The structure may include a central portion that is relatively thick and that extends radially a suificient distance for extension across a tube envelope and for engaging said tube envelope in seals involving1the two faces of this portion and the envelope. This thick portion may have a radius which disposes only a very narrow annular part thereof outside of the envelope. The structure also may include a relatively thin portion extending from said thick portion to the periphery of the disc structure. The thin portion referred tois therefore spaced from the seals engaging the thick portion aforementioned and the envelope.

This spacing is of appreciable significance according to the invention. Thus the thin portion of the disc outside of the tube envelope and disposed to receive impacts directed to the lead-in structure, may respond in con-siderable deformation to such impacts withoutin any way deforming the thicker portion of the lead-in. Theseals between such thicker portion and the tubeenvelope are therefore isolated from such impacts and preserved from the harm that would result if the full force of the impacts were transmitted to the regions of the seals.

The disc lead-in structure may include both portions referred to as integral parts thereof, orthe portions may .be two individual parts fixed to each other as: by welding or the portions may comprise twolayers fixed portion of disc to each other and a relatively thin portion fixed to the periphery of the layers at juncture region thereof. The preferred embodiment according to the invention is the aforementioned two part structure, its preference being dictated by ease of manufacture and by the fact that it provides a good protection for seals involving said structure and a tube envelope.

Referring now to the appended drawing for a better understanding of the invention,

Figure 1 shows a sectional elevation of an electron tube having the disc lead-in structure of the invention;

Figure 2 is an enlarged sectional view of a portion of the electron tube depicted in Figure l with the grid removed and shows the disc lead-in assembly of the invention sealed across an envelope; and

Figure 3 is a fragmentary sectional elevation of a modification of the disc lead-in structure of the invention.

While embodiments of the invention to be described in detail in the following, are of particular advantage when associated with the so-called Pencil type tube, the invention is adapted for use in other types of electron tubes utilizing disc lead-ins.

'In Figure 1 is shown a Pencil triode having an elongated envelope comprising at one end thereof a metal portion including a cylinder 11 having a flange 12. Within cylinder 10 is fixed a support 13 for a cathode 14, having a heater 15. The end of cylinder 11 remote from flange 12 is sealed by a glass stem 16.

At its other end, the envelope includes metal portion 17 including a cylinder 18 having a flange 19. Within cylinder 18 is mounted an anode 20. The end of cylinder 18 remote from flange 19 is closed by tipped-off exhaust tubulation 21. =1

The portion of the envelope between the metal end portions referred to comprises glass tubes 22, 23. One end of glass tube 22 is sealed to flange 19 and one end of glass tube 23 is sealed to flange 12. The glass tubes mentioned are of equal diameter and disposed coaxially to engage opposite faces of a disc lead-in assembly 24. The disc lead-in assembly referred to supports a grid 25.

The cathode 14, anode 20 and grid 25 are coaxially disposed and include coextensive portions constituting the effective parts of the three electrodes referred to.

It will be noted that the disc lead-in assembly is associated with the electron tube shown, in such a way, as to constitute a projection extending externally from the tube referred to. The assembly is therefore in a position to receive most of the impacts directed to the tube. In addition, the lead-in assembly aforementioned is sometimes called upon to resist appreciable forces applied to the tube when inserting it in a resonant line.

The impacts and forces referred to may be accompanied by serious effects on the electron tube discussed. One of these effects may take the form of ruptures in one or more of the several annular seals 26, 27, between the disclead-in assembly and the glass tubes 22, 23. Another of these effects may involve displacement of the grid 25, supported on the disc lead-in assembly, from co- -axial relation with the cathode 14 and anode 20.

T o prevent these undesirable and serious eflects, there is provided according to the invention, a novel disc leadin assembly. A preferred form of this lead-in assembly is shown in Figures 1 and 2. It includes a disc 30, made of silver plated steel for example, and having an appreciable thickness of the order of 50 mils. The central 30 is apertured to provide an opening 31 (Figure 2) having bevelled walls 32 to which the lower end of grid 25 is fixed as by welding. The disc 30 has a diameter slightly larger than that of the glass tubes 22, 23, to permit the glass tubes referred to to be sealed thereto in seals 26, 27, aforementioned, while avoiding an appreciable extent of the disc beyond the sides of said glass tubes. This disposes the disc 30 in a relatively ,shielded relation with respect to the electron tube in which it is used. Thus, it will be noted that the diameter of the disc 30 is only very slightly larger than that of the flanges 12, 19, so that the portions of the device including these flanges will share appreciably in absorbing impacts applied to .the tube envelope. This resultant distribution of the impacts will reduce the force of such impacts along one region of the device, such as the region of the disc 30, for example.

But while the reduction in diameter of the disc 30 is accompanied by the advantages above enumerated, it renders the device of reduced utility in association with a resonant line. Such use requires that the disc only, engage the inner surface of the line. In the structure so far described, there is danger that the flanges 12, 19 also may contact the resonant line and render the device inoperable in association therewith.

Therefore, according to a further feature of the invention, a flat and relatively thin ring or annular metal member 33 is fixed as by welding or brazing, .to a portion of disc 30 adjacent its periphery. The ring 33 is of less thickness than the disc 30, and may have a thickness of 10 mils. It is to be understood, however, that the ring referred to may have any thickness that is less than the thickness of the disc 30.

The ring 33, in the construction shown in Figures 1 and 2, has an inner diameter sufliciently smaller than the diameter of disc 30, to permit the ring to be affixed to one face of the disc as a convenience and for added strength. The outer diameter of the ring 33 is appreciably greater than the outer diameter of disc 30, to provide a disc assembly in which the ring referred to is adapted to contact the inner surface of a resonant line in such a way as to space appreciably .the flanges 12, 19 from such line.

The ring 33 is preferably provided with an offset portion 33a, which results in a cylindrical surface 33b having a diameter equal to the outer diameter of the disc 30. Engagement between the cylindrical surface 33b and the periphery of disc 30 will result in proper orientation of ring 33 axially with respect to disc 30. The offset portion 33a also provides a flat surface 33c on the ring 33 that is normal to the cylindrical surface 33b and that lies in a plane parallel to the plane of ring 33. This flat surface is adapted to abut against a face of disc 30 for properly orienting the ring 33 and disc 30 in a direction extending axially thereof. This construction of the ring 33 enables the disc 30 and ring 33 to be loosely assembled in desired positions prior to fixing the ring to the disc, without the use of added positioning jigs.

It will be noted that the two-piece disc lead-in described provides a device having a rugged support for grid 25 and is included in seals in such a manner as to minimize impairment of the seals. The outer portion of the disc lead-in assembly referred to formed by ring 33 is flexible to a greater degree than the disc 30, so that forces applied to the ring either in the form of impacts or incidental to inserting the device in or retracting it from a resonant line, are absorbed by the ring and thus prevented from reaching the disc 30. The disc 30 is therefore shielded from such forces by the ring 33. This preserves the seals 26, 27, from harm due to such forces, and assures a continued coaxial relation of grid 25 with the other electrodes aforementioned.

Instead of comprising two separate elements such as the disc 30 and ring 33, the disc lead-in assembly may be constituted of one integral structure of disc shape having a relatively thick central portion for supporting the grid and for engaging the glass tubes in the seals aforementioned, and having a relatively thin annular portion extending from the thick central portion to the periphery of the disc lead-in assembly. At present, however, it appears to be more economical to construct the disc lead-in assembly from two parts, i. e., the disc 30 and ring 33, than to make it an integral one part structure.

A further form of disc lead-in assembly is shown in Figure 3. In this form, the relatively thick central portion of the assembly comprises two thicknesses of material and includes two discs 34, 35, in superimposed face contacting relation and fixed to each other as by brazing or welding. In this construction, disc 34 may be provided with a cylindrical opening or passageway 36, and disc 35 may be provided with opening 37 coaxial with opening 36 and having bevelled walls 38 for facilitating fixing grid 35 to the lead-in assembly referred to.

Portions 39, 40 of the discs 34, 35 are bent away from each other as shown in Figure 3, to provide an annular recess 41 therebetween, for receiving a flat ring 42 hav ing a thickness less than the combined thickness of discs 34, 35, and preferably less than the thickness of one of the discs mentioned. The ring 42 may be fixed to discs 34, 35, in said recess as by welds or brazes 43, the structure lending itself particularly to brazing.

The outer diameter of ring 42 is appreciably greater than the diameter of the discs 34, 35, including the bent portions 39, 40 thereof. This disposes the ring in a less guarded position than the discs 34, 35, with respect to impacts directed to the tube structure in which the disc lead-in assembly is used. However, ring 42 is better adapted to absorb such impacts with reduced harm to seals 44, 45 due to the flexible character of the ring resulting from its reduced thickness in relation to the combined thickness of the discs 34, 35 which are engaged at said seals.

While'the embodiment shown in Figure 3 requires 3 parts and is therefore more expensive to make than the two part assembly shown in Figures 1 and 2, it possesses several advantages over the two part structure. cess 41 provides a pocket for brazing material, thus facilitating fixing the ring 42 to the discs 34, 35 by brazing. The recess referred to also aids desired orientation of the ring 42 in relation to the discs 34, 35. Of course, it is necessary to dispose the ring 42 in the recess mentioned, prior to fixing the discs 34, 35 to each other, since the inner diameter of ring 42 is less than the outer diameter of the discs 34, 35 including their bent portions 39, 40.

However, the two part structure shown in Figures 1 and 2 in addition to the aforementioned advantage of economy in manufacture, is also preferably to the three part structure in that it is free from the requirement of the three-part assembly of Figure 3 that the ring be loosely assembled in the structure prior to completion of assembly of the heavy disc portion thereof. Thus, the disc may be fully completed before the ring 33 is disposed in assembled relation with it. Moreover, the offset portion 33a provides normal surfaces 33b and 330, affording a satisfactory means for orienting the ring 33 with the disc 30.

It will be appreciated from the foregoing that the invention provides an electron tube of the disc seal type, wherein the disc assembly is constructed to reduce harm to seals with which it is associated.

The disc lead-in construction of the invention therefore contributes to ruggedness of a device in which it is used, and enables the device to withstand without harm, appreciably greater impact shocks than could be tolerated by prior art devices having disc lead-ins of equal thickness throughout.

What is claimed is:

1. An electron tube having an envelope portion of insulating material and a metallic disc lead-in extending through said envelope, said disc lead-in comprising a relatively rigid central portion having a thickness of the order of 50 mils, and a relatively flexible annular peripheral portion having a thickness of the order of 10 mils, said central portion only, engaging said envelope in a seal, said peripheral portion being spaced from said seal, whereby said peripheral portion is adapted to absorb The re- 6 yieldingly, stresses applied to the periphery of said lead-in for preserving said seal from harm.

2. An elongated electron tube having an envelope comprising a tubular metallic cylinder at one end thereof, another tubular metallic cylinder at the other end thereof, a metallic lead-in element disposed between said cylinders, and two tubular insulating elements each disposed between and fixed to said lead-in element and one of said cylinders; said lead-in element comprising an annular, relatively fiat and rigid central member fixed to said insulating elements in seals and having a portion extending into said envelope and supporting an electrode thereon, and only one annular, relatively flat peripheral member outside of said envelope and permanently fixed to said central member and spaced from said seals along a plane normal to the long axis of said tube and outwardly from the outside surfaces of said insulating elements and adapted to engage forcefully a circuit element, said peripheral member being appreciably more flexible than said central member and adapted to respond to deformation to a forceful engagement therewith and the outer transverse extent of said peripheral member being appreciably greater than the outer transverse extent of said central member providing a lead-in element in which said peripheral member insulates said central member and said insulating elements from forces applied to said peripheral member.

3. An elongated electron tube having an envelope comprising a tubular metallic cylinder at one end thereof, another tubular metallic cylinder at the other end thereof, a metallic lead-in element disposed between said cylinders, and two tubular insulating elements each disposed between and fixed to said lead-in element and one of said cylinders; said lead-in element comprising an annular, relatively flat and rigid central member fixed to said insulating elements in seals and having a portion extending into said envelope and supporting an electrode thereon, and only one annular, relatively flat peripheral member outside of said envelope and permanently fixed to said central member and spaced from said seals along a plane normal to the long axis of said tube and outwardly from the outside surfaces of said insulating elements and adapted to engage forcefully a circuit element, said peripheral member being appreciably more flexible than said central member and adapted to respond in deformation to a forceful engagement therewith and the outer transverse extent of said peripheral member being appreciably greater than the outer transverse extent of said central member providing a lead-in element in which said peripheral member insulates said central member and said insulating elements from forces applied to said peripheral member, said central member having a cylindrical outer surface parallel to said tube axis and having a flat surface in a plane normal to said axis, said peripheral member having an offset portion providing a cylindrical surface abutting said cylindrical surface of said central member, said peripheral member including a portion thereof having a flat surface engaging said fiat surface of said central member, whereby said engagement of said cylindrical surfaces provides coaxial orientation of said members with respect to each other and said engagement of said flat surfaces provides parallel orientation of said members with respect to each other thereby to facilitate an assembly of said members in desired relative orientation prior to fixing said members to each other.

References Cited in the file of this patent UNITED STATES PATENTS 1,850,104 Hansell Mar. 22, 1932 2,284,405 McArthur May 26, 1942 2,367,331 Bondley Jan. 16, 1945 2,397,854 Glauber Apr. 2, 1946 2,416,565 Beggs Feb. 25, 1947 2,481,026 Law et al. Sept. 6, 1949 

